| 1. |
- Andersson Granberg, Tobias, et al.
(författare)
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A framework for integrated terminal airspace design
- 2019
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Ingår i: Aeronautical Journal. - : CAMBRIDGE UNIV PRESS. - 0001-9240 .- 2059-6464. ; 123:1263, s. 567-585
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Tidskriftsartikel (refereegranskat)abstract
- Route planning and airspace sectorisation are two central tasks in air traffic management. Traditionally, the routing and sectorisation problems were considered separately, with aircraft trajectories serving as input to the sectorisation problem and, reciprocally, sectors being part of the input to the path finding algorithms. In this paper we propose a simultaneous design of routes and sectors for a transition airspace. We compare two approaches for this integrated design: one based on mixed integer programming, and one Voronoi-based model that separates potential "hotspots" of controller activity resulting from the terminal routes. We apply our two approaches to the design of Stockholm Terminal Maneuvering Area.
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| 2. |
- Fentaye, Amare Desalegn, et al.
(författare)
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Gas turbine prognostics via Temporal Fusion Transformer
- 2024
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Ingår i: Aeronautical Journal. - : CAMBRIDGE UNIV PRESS. - 0001-9240.
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Tidskriftsartikel (refereegranskat)abstract
- Gas turbines play a vital role in various industries. Timely and accurately predicting their degradation is essential for efficient operation and optimal maintenance planning. Diagnostic and prognostic outcomes aid in determining the optimal compressor washing intervals. Diagnostics detects compressor fouling and estimates the trend up to the current time. If the forecast indicates fast progress in the fouling trend, scheduling offline washing during the next inspection event or earlier may be crucial to address the fouling deposit comprehensively. This approach ensures that compressor cleaning is performed based on its actual health status, leading to improved operation and maintenance costs. This paper presents a novel prognostic method for gas turbine degradation forecasting through a time-series analysis. The proposed approach uses the Temporal Fusion Transformer model capable of capturing time-series relationships at different scales. It combines encoder and decoder layers to capture temporal dependencies and temporal-attention layers to capture long-range dependencies across the encoded degradation trends. Temporal attention is a self-attention mechanism that enables the model to consider the importance of each time step degradation in the context of the entire degradation profile of the given health parameter. Performance data from multiple two-spool turbofan engines is employed to train and test the method. The test results show promising forecasting ability of the proposed method multiple flight cycles into the future. By leveraging the insights provided by the method, maintenance events and activities can be scheduled in a proactive manner. Future work is to extend the method to estimate remaining useful life.
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| 3. |
- Gerdes, Mike, et al.
(författare)
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Fuzzy Condition Monitoring of Recirculation Fans and Filters
- 2011
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Ingår i: Aeronautical Journal. - Vienna : Springer. - 0001-9240 .- 1869-5582 .- 1869-5590. ; 2:1-4, s. 81-87
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Tidskriftsartikel (refereegranskat)abstract
- A reliable condition monitoring is needed to predict faults. Pattern recognition technologies are often used for finding patterns in complex systems. Condition monitoring can also benefit from pattern recognition. Many pattern recognition technologies, however, only output the classification of the data sample but do not output any information about classes that are also very similar to the input vector. This paper presents a concept for pattern recognition that output similarity values for decision trees. The concept can be used on top of any normal decision tree algorithms and is independent of the learning algorithm. Performed experiments showed that the concept is reliable and it also works with decision tree forests to increase the classification accuracy.
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| 4. |
- Jansson, Natascha, et al.
(författare)
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Steady and unsteady pressure measurements on a swept-wing aircraft
- 2014
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Ingår i: Aeronautical Journal. - 0001-9240. ; 118:1200, s. 109-122
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Tidskriftsartikel (refereegranskat)abstract
- Steady and unsteady pressure measurements are conducted for a tailless aircraft model. The main aim with the presented experimental work is to investigate the difficulties and possibilities involved in using an available pressure sensing system for accurate unsteady pressure measurement. The experimental procedure which is utilised for unsteady pressure measurements is described in detail. In particular, the importance of synchronised timing is recognised. For a harmonically varying pressure a small time delay in the measurement chain can result in a significant phase shift. Also, difficulties and uncertainties that are still present are pointed out. The results from these experiments are compared to numerical results based on unsteady potential flow theory. In general, the experimental and computational results show similar trends. Especially good agreement is found for the steady pressure measurements. For the unsteady pressure measurements a possible Reynolds number dependency is found for the considered test conditions.
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| 5. |
- Kyprianidis, Konstantinos, et al.
(författare)
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Dynamic performance investigations of a turbojet engine using a cross-application visual oriented platform
- 2008
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Ingår i: Aeronautical Journal. - 0001-9240. ; 112:1129, s. 161-169
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the development of visual oriented tools for the dynamic performance simulation of a turbojet engine using a cross-application approach. In particular, the study focuses on the feasibility of developing simulation models using different programming environments and linking them together using a popular spreadsheet program. As a result of this effort, a low fidelity cycle program has been created, capable of being integrated with other performance models. The amount of laboratory sessions required for student training during an educational procedure, for example for a course in gas turbine performance simulation, is greatly reduced due to the familiarity of most students with the spreadsheet software. The model results have been validated using commercially available gas turbine simulation software and experimental data from open literature. The most important finding of this study is the capability of the program to link to aircraft performance models and predict the transient working line of the engine for various initial conditions in order to dynamically simulate flight phases including take-off and landing.
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| 6. |
- Källström, Johan, et al.
(författare)
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Design of simulation-based pilot training systems using machine learning agents
- 2022
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Ingår i: Aeronautical Journal. - : Cambridge University Press. - 0001-9240 .- 2059-6464. ; 126:1300, s. 907-
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Tidskriftsartikel (refereegranskat)abstract
- The high operational cost of aircraft, limited availability of air space, and strict safety regulations make training of fighter pilots increasingly challenging. By integrating Live, Virtual, and Constructive simulation resources, efficiency and effectiveness can be improved. In particular, if constructive simulations, which provide synthetic agents operating synthetic vehicles, were used to a higher degree, complex training scenarios could be realised at low cost, the need for support personnel could be reduced, and training availability could be improved. In this work, inspired by the recent improvements of techniques for artificial intelligence, we take a user perspective and investigate how intelligent, learning agents could help build future training systems. Through a domain analysis, a user study, and practical experiments, we identify important agent capabilities and characteristics, and then discuss design approaches and solution concepts for training systems to utilise learning agents for improved training value. © The Author(s).
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| 7. |
- Martensson, H., et al.
(författare)
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Design of a sub-scale fan for a boundary layer ingestion test with by-pass flow
- 2022
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Ingår i: Aeronautical Journal. - : Cambridge University Press (CUP). - 0001-9240 .- 2059-6464. ; 126:1302, s. 1288-1302
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Tidskriftsartikel (refereegranskat)abstract
- A design of a sub-scale Boundary Layer Ingestion (BLI) fan for a transonic test rig is presented. The fan is intended to be used in flow conditions with varying distortion patterns representative of a BLI application on an aircraft. The sub-scale fan design is based on a design study of a full-scale fan for a BLI demonstration project for a Fokker 100 aircraft. CFD results from the full-scale fan design and the ingested distortion pattern from CFD analyses of the whole aircraft are used as inputs for this study. The sub-scale fan is designed to have similar performance characteristics to the full-scale fan within the capabilities of the test facility. The available geometric rig envelope in the test facility necessitates a reduction in geometric scale and consideration of the operating conditions. Fan blades and vanes are re-designed for these conditions in order to mitigate the effects of the scaling. The effects of reduced size, increased relative tip clearance and thicknesses of the blades and vanes are evaluated as part of the step-by-step adaption of the design to the sub-scale conditions. Finally, the installation effects in the rig are simulated including important effects of the by-pass flow on the running characteristics and the need to control the effective fan nozzle area in order to cover the available fan operating range. The predicted operating behaviour of the fan as installed in the coming transonic test rig gives strong indication that the sub-scale fan tests will be successful.
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| 8. |
- Nguyen, S.N., et al.
(författare)
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Improved models for runway debris lofting simulations
- 2009
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Ingår i: Aeronautical Journal. - 0001-9240. ; 113:1148, s. 669-681
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Tidskriftsartikel (refereegranskat)abstract
- Numerical models used to simulate the lofting mechanisms of runway stones were developed to assess the threat to aircraft structures from runway debris impacts. An inflated aircraft tyre model, which was validated by comparison with experimental indentation tests, showed that over-rolling of stones under typical take-off conditions led to only modest vertical loft velocities of less than 5 m/s. Experiments using a drop weight impactor simulated a section of aircraft tyre descending upon stones. These tests demonstrated that lofting was achieved for impacts with low rubber thickness. However, for impacts with greater rubber thickness, lofting was suppressed. Using more realistic tyre geometries resulted in launches with backspin, but only horizontally along the ground in the direction of the tyre axis. The speed at which launches occurred was proportional to the rate of descent of the tyre section and would consequently determine the loft speeds due to potential asperity lofting.
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| 9. |
- Nguyen, Sang N., et al.
(författare)
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Runway debris impact threat maps for transport aircraft
- 2014
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Ingår i: Aeronautical Journal. - 0001-9240. ; 118:1201, s. 229-266
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Tidskriftsartikel (refereegranskat)abstract
- Large transport aircraft are particularly susceptible to impact damage from runway debris thrown up by the landing gear. A methodology was developed to predict the trajectories of stones lofted by the nose wheel and subjected to aerodynamic forces due to the wake behind the nose landing gear and beneath the aircraft. In conjunction with finite element modelling of the stone/ground/tyre contact mechanics, an analytical model was used to perform a stochastic prediction of the trajectories of runway stones to generate impact threat maps which showed the relative likelihood of stones impinging upon various areas on the underside of a C-130 Hercules. The impact envelopes for the C-130 extended three to eighteen metres behind the nose wheel and two metres either side of the centre of the aircraft. The impact threat maps were especially sensitive to the values of the coefficients of lift and drag acting on the stone during its flight.
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| 10. |
- Olsson, Robin
(författare)
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Modelling of impact damage zones in composite laminates for strength after impact
- 2012
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Ingår i: Aeronautical Journal. - : Royal Aeronautical Society. - 0001-9240. ; 116:1186, s. 1349-1365
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Tidskriftsartikel (refereegranskat)abstract
- This paper reviews findings on the type, morphology and constitutive behaviour of impact damage zones during loading after impact and their effect on the laminate strength and stability. The paper is limited to tape prepreg based monolithic laminates, although some similarities exist with impact damage in textile based laminates. Damage zones have a complex geometry with several damage types, which results in an interaction and competition between different failure mechanisms, e.g. local and global buckling, compressive failure, and delamination growth. Hence, simplified damage models may provide incorrect predictions of the failure load and failure mechanisms after impact. The constitutive behaviour of damage zones has been studied experimentally in tension and compression using an inverse method, and the results have been compared with detailed FE models of a generic impact damage. The paper is concluded with a discussion on analytical and computational models to predict the resulting strength of impacted laminates.
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